In this blog post, we will look at the scientific principles behind lasers and how they have brought about innovation in our daily lives in areas such as medicine, industry, and communications.
LASER is an acronym for “Light Amplification by Stimulated Emission of Radiation,” which means “amplifying light by inducing radiation.” Lasers originally referred to the physical phenomenon of light amplification, but now refer to devices that generate laser beams. The concept of lasers was conceived in 1951 by Charles Townes based on Einstein’s theory of radiation wave generation, and in 1960, Theodore Maiman built the first laser device. This marked a revolutionary development in science and engineering, and lasers are now used in a wide range of fields.
Atoms are composed of atomic nuclei and electrons, with electrons arranged around the nucleus according to their energy levels, which can be likened to steps or a ladder. As the energy level rises, the energy possessed by the electrons also rises, and electrons with lower energy levels fill the energy levels closer to the nucleus. When an electron absorbs external energy, it leaves its position and rises to a higher energy level. The state in which an electron is in its position is called the “ground state,” and the state in which it has risen to a higher energy level is called the “excited state.” Electrons in the excited state tend to return to the ground state, and when they return to their original position, they emit energy in the form of light. This principle allows us to explain various phenomena related to energy transfer.
Mayer, who created the first laser device, used electrons in rubies. This was because rubies have the characteristic of allowing electrons to remain in an excited state for a long time. Mayer excited specific electrons in ruby by shining light on it, creating more excited electrons than electrons in the ground state. When this state is created, at least one excited electron naturally returns to its original energy level, emitting light, and other excited electrons emit light of the same wavelength in turn. Meanwhile, the light generated between the two mirrors installed on both sides of the excited material is reflected as is, traveling back and forth several times and inducing other excited electrons to emit light. As a result, the light is continuously amplified. At this point, one of the two mirrors allows some of the light to pass through, and some of the amplified light between the mirrors is emitted to the outside as a laser beam. This process explains the basic operating principle of lasers and is important for understanding the concept of optical amplification.
Since the development of Maiman’s ruby laser, many types of lasers have been created using gases, liquids, solids, semiconductors, and other media, and their characteristics vary widely. However, all laser beams are basically composed of photons with a single wavelength and directionality, and they travel in a nearly perfect straight line without spreading in other directions. In addition, light can be focused on an extremely small point through a lens. This is a major difference from ordinary light, which consists of various photons, spreads easily in different directions, and cannot be easily converged through a lens. Thanks to these characteristics, lasers have become a core technology in various scientific and industrial fields.
Based on these characteristics, laser beams can do things that ordinary light cannot. They can display desired letters or beautiful images in the air and play music from CDs. In manufacturing, laser beams are used to precisely cut or burn various objects, and doctors use laser beams in surgery. They also function as a communication medium that can carry a huge amount of communication information in a unit of time. For example, fiber optic technology using lasers enables high-speed Internet connections, contributing to the information society of today. Lasers have established themselves as a cutting-edge technology that has a tremendous impact on almost all products and services today. Through this, we can expect a better quality of life and innovative technological developments.
